Valentines Day Mystery
by Turtlegirl5
Summary: It's Valentines Day and Phineas has found a mysterious love letter on his locker. This leads to becoming a detective again to figure out who his secret admirer is. Meanwhile, Perry is trying to rid of a terrible laughing gas.
1. Chapter 1

**Important! If you have ****NOT**** read the story, "Phineas and Ferb: School Days A new series" yet, I highly recommend you read that before you read this. I've decided to put this message up to avoid any confusion.**

Chapter 1

Isabella walked up to Phineas Flynn and asked him sweetly, "What cha' doin'?"

"I'm so glad you're here, Isabella!" Phineas exclaimed. "I just finished building our dream castle where we can be together forever!"

A rainbow bridge appeared in front of the two. Then, a beautiful white unicorn pranced over. Phineas got on and helped Isabella up as well.

"Happy Valentines Day, Isabella."

"Oh this is the best Valentines Day ever!" Isabella gasped.

They arrived at the magical palace that Phineas had built.

"One last thing. A gift for you, my love." Phineas handed Isabella a small pink package. She opened it and inside was a digital clock! The alarm went off. Beep! Beep! Beep! Beep!

"What?"

Isabella woke up. She sat up in her bed.

"Oh. It was just a dream," she said to herself. "But it's Valentines Day!" She jumped out of bed and quickly got dressed and brushed her hair.

"Today, I'm going to ask Phineas to my Valentine. But how should I do it, Pinky?" Isabella asked her Chihuahua.

"Hmmm… Maybe I should leave a note on his locker. Kind of old school, but soooo romantic! Soooo mysterious! It'd be perfect!" Isabella said dreamily.

Pinky barked happily in reply.

Isabella went to school early. She sealed her envelope with a sticker and a kiss and then stuck it on Phineas' locker.

Later, Phineas and Ferb walked to their lockers.

"Really, Ferb? I never knew that! Huh… Well, I guess that's why they call it- Hey! What's this?" Phineas said. He took the pink envelope off of his locker. He opened it up.

He read aloud:

Dear Phineas,

Will you be my valentine? I know it's kind of a sudden thing, and I know it's kind of cheesy, but I really want to know. This is kind of hard for me to write because I'm trying to make this as awkwardless as possible. Is that even a word? Hmm… I should look it up in the dictionary. Well, I know what you're going to do today. You're going to reply to this letter!

Secret admirer

P.S. If you want to respond and want to find out who I am put a reply on locker 117. Please do it!

Phineas looked at the letter strangely. He said, "Well, that was written really funny. The person was probably just nervous. I have no idea whose locker that is. Ferb, I know what we're going to do today. We're going to be detectives again! I know it's kind of against the code, but this'll be fun! Especially when we already have our first clue!"

Phineas sniffed the letter.

"It smells like vanilla. Better write this down."

Ferb took out a piece of paper and started scribbling all over it.

Little did they know, one of the fireside girls was standing around the corner listening in…

The girl down a few hallways and met up with Isabella and the rest of the troop.

"He's got the letter and he's going to try to figure out who it is!" she cried.

All of the girls squealed.

"Is he going to leave a reply?" Isabella asked excitedly.

"Actually, he's setting up a whole detective thing to figure it out."

All the girls let out a disappointed, "Awwwww…"

"Shouldn't you just to tell him, Isabella?" Holly asked.

"I don't know. It's not very romantic when I just tell him. I want to keep it a mystery. Knowing him, he's going to figure it out. This is so exciting though! Eeeep!" Isabella said.

The girls squealed again.


	2. Chapter 2

Chapter 2

Carl ran in between second and third period to pick up Perry. He took him outside to a secret tunnel under a tree. Perry looked up at Carl who looked like he was in kind of a bad mood. Carl looked back down at him and said, "What, Agent P? I know it's Valentines Day! Don't make fun of me! I deserve love!"

Carl threw Perry down the chute. The platypus looked confused for a moment, but then remembered Carl's relationship status.

Perry arrived at the agency and sat down in the chair in front of the big screen. Monogram's face appeared on it.

"Good morning, Agent P. And happy Valentines Day. Knowing Doofenshmirtz, he's going to want to destroy Valentines Day in some sort of way, so get to the bottom of it. Good luck."

Perry saluted and headed off.

Phineas went down to wood shop where Ferb's last class was.

"So how's it going in wood shop, Ferb?" Phineas asked. Ferb handed him a progress report.

"Straight A's. Doesn't surprise me a bit." Phineas walked down an aisle between two tables. Each lined up with wooden log cabin coin banks.

"Which one did you make, Ferb?"

Ferb pointed to the big one on the end. It looked more like a castle and when you pressed a button a little, wooden Abraham Lincoln figure would come out the door, say how much money was in the bank, and go back in.

"Sweet." Phineas and Ferb went to the teacher's desk.

"Can we use your robot and mechanic stuff? We need to build something to help us with a case- a love case."

The teacher replied, "Well, this equipment are for the eighth and above graders so aren't you a little young to be using this stuff?"

"Yes. Yes we are."

"Well, since Ferb here is such a good student, why not?"

"Thanks."

Phineas and Ferb got to work. They worked on it in between class periods. Finally, they finished just before lunch.

Meanwhile, Candace was walking through the halls with her friends. She jumped up and down the whole time screaming to the world, "I HAVE A VALENTINE!"

Stacy said softly, "I know it's a relief to not have that pressure of the whole, 'will you be my valentine' thing. But the entire school does not have to know."

"Yea, besides. Don't you think that would be a little embarrassing to Jeremy?" Vanessa asked.

"I'm sure he's proud. I'm actually doing him a favor. He doesn't have to spread the word because I'm doing it for him," Candace proclaimed.

"Alright then," Stacy and Vanessa said in unison. Candace twirled like a ballerina and said, "What could possibly ruin this glorious day?"

Right that moment, a small robot dog pounced on Candace, pinning her to the ground.

"What the!?"

The dog started sniffing her all over.

Phineas and Ferb came over wearing trench coats.

"Oh hey, Candace. Looks like you met Whiff. We were planning on making a bigger one over the summer, but we didn't really have time. And he doesn't do the same job."

"Phineas! Ferb! What is this all about?" Candace cried. The dog got off of Candace and ran over to Stacy then Vanessa, sniffing them all over.

"Well, this morning I got a Valentines letter from a secret admirer. We're trying to figure out who it is. Whoever it is, they smell like vanilla. So we're having Whiff here sniff her out," Phineas explained.

"Where'd you get the outfits?" Vanessa asked.

"Drama department," Phineas answered.

Candace stood up slowly and asked, "_You_ have a secret admirer? Let me see the note!"

Ferb handed it to her from his pocket. Candace read it. She nodded a few times.

"Uh-huh… uh-huh… What are you two's problem? Why couldn't you just simply go to locker 117 instead of attacking all the girls with a robotic dog?"

"Well, what's the adventure in that? Just showing up at her locker? Meeting by the locker is so old school and then it just gets really sappy from there," Phineas said.

"Uh, how do you know all this?" Vanessa asked.

"That's the mystery," Ferb said with a wink.

Phineas said, "We need to go to lunch now. This will be the perfect opportunity to have Whiff scan everyone."

**Glad you all are liking it. I may not be able to update every day since I'm so swamped with homework every night, but I'll try my best.**


	3. Chapter 3

Chapter 3

Doofenshmirtz Evil Incorporated…

Perry burst through the door of his nemesis' apartment.

"Perry the Platypus!" Dr. Doofenshmirtz exclaimed as he approached the platypus. He handed him a pink card and a box of chocolates. He said, "Some girl stopped over and wanted me to give these to you from her for Valentines Day. I think I know what that means."

Perry took the gifts coolly and read the card. When the card was opened, a sensor went off and a thorny cage of roses fell on top of him.

"Ha! I tricked you, Perry the Platypus. There was no girl! It was really I that gave you the roses and card. Which is kind of awkward… Anyway, get ready for my evil plan. Those chocolates _are _edible though, so feel free to eat some while I tell you my back story."

Perry opened the box and nibbled on the heart-shaped candies.

Doofenshmirtz sat down and began, "It all started on Valentines Day years ago. I was madly in love with this girl who loved the beach. We went to the beach a lot together. I even still have this snow globe from the beach gift shop. See? It's filled with real salt water from the beach. I don't understand why they would have _snow _globes at a beach. I mean, why would it snow on the beach? Anyway, the thing that she loved more than the beach were funny men. So I decided to try and impress her by learning stand-up comedy. I was going to perform at one of those hip dinner theaters on Valentines Day. But when I did my act nobody thought I was funny. Not a single laugh."

Within Dr. D's back-story, Doofenshmirtz was on a stage with a microphone he attempted a joke, "So what's up with airline food? Huh? Huh?" Crickets began to chirp.

Dr. Doofenshmirtz continued his story, "It broke my heart and I was humiliated all at the same time! So behold, the Ha-ha-hainator! I just need to use this pump to spread this laughing gas across the entire Tri-state area! Then, anyone who inhales it within ten seconds after I spread it will laugh non-stop! Their sides will hurt from laughing so hard! So because they didn't laugh at my jokes they will have to pay by laughing uncontrollably!"

Perry's eyes widened.

"Before that happens, I need to keep working on the Ha-ha-hainator. It's not quite ready yet. Don't go anywhere, Perry the Platypus. Oh wait, that's right. You can't!" Doofenshmirtz laughed.

"See? That's funny. Because why would you go anywhere when you're trapped in a thorn cage?"

There was a silence.

"Don't say anything. I know! I'm not funny."

Meanwhile, at lunch, Phineas and Ferb explained their whole plan to their friends.

Isabella smiled and said, "Wow. What a great idea. I bet that whoever left you that note is _really _cute. I mean she even dots her I's with hearts."

Baljeet asked, "How will you know which one is her? I mean I'm sure that there are a lot of girls in this school that smell like vanilla."

"We're not sure yet. We'll just narrow it down from there," Phineas said.

Whiff ran around the lunchroom sniffing everyone. Isabella said loudly, "Mmm-mmmm! I sure _love_ this _vanilla _ice cream."

Her fireside friend, Milly, added, "Here, Isabella, have this _vanilla _cookie. I know how much you like _vanilla._"

Katie asked, "What kind of shampoo do you use, Isabella?"

"I use _vanilla _scented," Isabella answered.

The girls all looked at Phineas who was looking in the other direction. He turned to look at them.

"What?" he asked.

"Didn't you hear any of that?" asked Gretchen.

"Oh. Sorry. I was so busy watching Whiff. I didn't know you were talking to me," Phineas answered.

The girls all sighed. Just then, Whiff ran up to Isabella and jumped up and down. He barked happily.

"Hey, Whiff is barking at me! I must be the one!" Isabella cried. "Now before, I go into detail about everything, I want to know how you feel about it."

Phineas grabbed Whiff.

"Feel about what? It was probably just a glitch thing. Whiff probably just smelled your vanilla ice cream and mistook it for you," Phineas said.

There was a brief pause when Adyson tried to start the hinting again. She said, "Hey, Isabella. I forget. What is your locker number again?"

"Oh it's one seventeen!" Isabella answered.

"Oh yeah! How could I have forgotten?"

They all looked over to where the boys were, but to find they were gone. The cafeteria was already headed outside.

The girls sighed again and headed out to find Phineas and Ferb with a giant machine.


	4. Chapter 4

Chapter 4

"Well, that was fast," Isabella said.

"Yep. That fast forward remote really comes in handy," Phineas said.

Isabella put her hands behind her back and said, "Sooo… Whatcha' doin'?"

Phineas held out his arms towards the machine.

"Ta-da! We're going to have every girl on the playground go through this machine. Whiff will give them a good whiff and then, they have to write, 'I like vanilla' on a piece of paper with their name on it. Then, we give the papers to this machine over here. The machine will store every piece of writing and compare each of them to the secret admirer note," Phineas explained.

"Oh wow. Does _every_ girl have to go in?" Isabella asked.

"Yep. Just to be on the safe side."

Isabella turned back to her friends and smiled. They went to the end of the line.

Meanwhile…

Perry pulled out some goggles, gloves, and some gardening sheers. He put the goggles and gloves on and began snipping his way through the thorns of his rose cage.

"You know, what is it about some comedians that are so funny? Why do people laugh at them? What's the difference between their jokes and mine? I- I just don't get it," Dr. Doofenshmirtz complained.

"Maybe people are too entertained by fart jokes now a days. What do you think, Perry the Platypus?"

Dr. D looked at the platypus who quickly hid his gardening gear behind his back.

Back at the school time had flown by a bit.

Candace was still talking away.

"And then Jeremy and I will get married and have two kids named Xavier and Amanda!" she cried.

Vanessa moaned, "We know. You told us about twenty times already."

Stacy said, "Hey. You do know that if for some reason you ever actually _do _marry Jeremy, that Little Susie would end up being your sister-in-law. Don't you?"

Candace's smile faded and her eyes widened in horror. There was a long silence after that. Finally, Candace looked out the window and saw Phineas and Ferb's invention.

"What are they- Ya know what? I'm not even going to say it. It's Valentine's Day. I should be focusing on Jeremy."

Stacy and Vanessa both groaned.

Isabella was nearing the front of the line. Ferb stacked all the possibilities that the machine had printed out together.

"Yes! I'm next!" Isabella cried. Just then, the whistle blew and everyone had to line up.

"Whoops. Sorry girls," Phineas said. "If we can't figure it out from this stack, we'll try to figure it out from there on what to do."

Isabella was getting really frustrated. She tried her best to be patient though. During their next period classes, they both worked on narrowing down the possibilities the computer had made.

On the other hand, Isabella met with some of her friends again. "She said, you know, this is getting way out of hand. Maybe I should just tell him it was me."

"Why?" Katie asked.

"Phineas apparently is not going to figure it out and I just want to get it done with. I'll meet him at his locker after class."

Meanwhile…

"Almost done. And… here it is! Behold the Ha-ha-hainator!" Doofenshmirtz held it up.

"Get ready to meet your laughing doom!" Doofenshmirtz began pumping the gas out the window.

Perry's eyes widened he continued to slice through the thorns, but when he escaped it was too late.

XXXX

Isabella walked down the hall towards Phineas' locker. "Just do it, Isabella. You can do it," she told herself. She hiccupped. "Well, after I get rid of these hiccups. I want to *hiccup* make sure he can take me ser-*hiccup*iously." Isabella held her breath for ten seconds, which at the very same moment was when the gas had traveled to the school.


	5. Chapter 5

Chapter 5

Isabella released her breath again. Her hiccups were gone. "That's better," she said. She approached Phineas and Ferb. For some reason everyone around her began laughing.

"Hey, Phineas?" she asked.

Phineas turned around with a huge smile. He chuckled, "Oh. Hey, Isabella. What's up?"

"Well, you know that secret admirer note? I know who wrote it."

"Oh do you?" Phineas said in an unsure way.

"Well, I-" Isabella was interrupted by Phineas and Ferb's snickering.

"What's so funny?"

"We don't know. We just all of a sudden feel like laughing!" They both started laughing out loud along with the rest of the kids in the hallway.

Isabella looked around she didn't see anything funny. She looked down at her outfit and looked in the mirror of Phineas' locker. There wasn't anything funny about her.

"I wanted to let you know that the secret admirer note was-"

Soon the boys were both practically on the ground laughing. Isabella started to get mad.

"Oh! My sides hurt!" Phineas continued laughing. "It feels as if some hands just out of no where came over and are tickling my stomach without stopping!" The whole hallway was laughing on controllably, but no one knew why.

"Phineas! Will you just listen to me!?" Isabella cried. "I left you the secret admirer note! I'm your secret admirer! It's me! Isabella Garcia-Shapiro! Understand!?"

Phineas and Ferb stopped laughing and looked up at her. Isabella's face softened. There was a pause, then Phineas and Ferb both started cracking up again.

"Why won't they take me seriously?" Isabella asked aloud, knowing that if she asked them, they wouldn't answer.

Phineas stood up wiping a tear from his face.

"Phew! The bell's going to ring soon. Better get to class." They both skipped off laughing their heads off along with the rest of the school like a pack of hyenas.

Isabella looked down sadly. She wanted to cry.

(Song time! It's a sad love song)

Meanwhile…

"You are too late, Perry the Platypus! Everyone in the tri-state is now laughing hysterically! And now it's your turn!" Dr. Doofenshmirtz held his breath and aimed the pump towards Perry and sprayed it. Perry jumped out of the way holding his breath as well.

Dr. D barely shouted trying not to release his breath, "Get back here Perry the Platypus!"

He continued spraying. "Perry the Platypus, you must have a huge lung capacity. You haven't given up- oh no! I breathed it in now I'm going to- hahahahahha!" Doofenshmirtz began laughing.

"Now, I'm going to- hahahahhahahahahah!" Dr. D grabbed his stomach. "Oh! This hurts! Oh!"

Still laughing hard, Doofenshmirtz grabbed the pump and continued spraying the gas everywhere.

"You can't hold your breath forever Perry the- hahahahahhah! What is with the word 'platypus' it's such a funny word. Who came up with it?"

Perry's face was turning blue. He couldn't hold his breath any longer. He finally released it. Dr. D immediately began spraying again. Perry accidentally inhaled and began chatting in a chuckling sort of way.

He jumped around trying to avoid Doofenshmirtz. Dr. D grabbed him and spun him around, thus him crashing into the sofa. Perry hit his head pretty hard. Though it was more painful than ever, he continued to laugh.

"Perry the Platypus, you broke my couch!" There was a small pause and then the two both started chortling again.

Perry had to think quickly on how to get rid of this excruciating laughter. He tried to think of sadness, which was difficult to do due to the fact that he could stop chattering in joy. He thought of tears. Tears were made of salt water. Maybe the smell of salt water would mellow the mood.

The platypus looked around the room and spotted the souvenir beach snow globe that Dr. D had mentioned before, had actual salt water from the beach in it. Perry grabbed it and took the spray pump.

"Perry the Platypus- oh there's that funny word again!- what are you doing!?" Doofenshmirtz said through his laughter.

Perry broke open the snow globe and poured the water in. The strange pump- inator machine would turn the liquid into a gas and spread the smell over the tri-state area.

Perry ran to the window and pumped the smell of salt water into the air. Then, he pumped it into the room.

The two breathed it in and the laughter stopped.

"How did you do that, Perry the Platypus? That doesn't make any sense. How could the ocean make people stop laughing?*****" Doofenshmirtz asked.

Perry shrugged. He jumped out the window and parachuted down to the ground. He noticed his hat had a couple of roses stuck to them by their thorns from the cage. He took them out and held them between his teeth as he landed.

"And that doesn't make any sense either! You didn't have that back pack when you came in here!" Dr. D called. "Aw well. Gee, I feel a kind of sadness right now. All that laughing really makes you tired."

Back at school…

Candace's laugh soon faded. "That was weird. What was so funny? All of a sudden I feel kind of sad."

Vanessa's giggle calmed down too. "Oh brother. That was probably my dad again."

"How can you tell?" asked Stacy.

"If something ever weird happens just clear out of the blue, it's definitely him."

"Did you guys notice something? I haven't tried to bust my brothers at all today!" Candace exclaimed.

"So?" Stacy asked.

"So! I need to do something about that. They are so busted when I get home for that robot dog! I'm not going to bother with Principal Tom today." Candace cried.

**Note: *cartoons will be cartoons. **


	6. Chapter 6

Chapter 6

Perry, on his way back to the school, rode past Isabella's cousin's house, who also owned a pet platypus named Patty who he had teamed up with once before*****. He figured that he had the roses, so might as well do something with them.

He took a deep breath and went to the backyard where a sleeping, purple platypus was. She drowsily opened one eye, but as soon as she saw it was him, sprang to her feet. He handed her one of the roses he had taken from Doofenshmirtz's. Patty's face lit up. She immediately hugged him. Perry rolled his eyes a little. Once she let go, Perry smiled painfully after that tight embrace and headed off again. Patty certainly had her day made.

As Perry headed back off to school, he wondered what to do with this other rose…

The end of the school day rolled around. When Phineas and Ferb got home, Candace ran through the door. Their mom was reading the mail.

"Mom! Come look! Phineas and Ferb built a robot dog today to attack all the girls in school! It acts like a real dog too! It's not like one of those choppy robot toys that you see at the store! It's really realistic except for the metal and robot-y look to it! But come on! They're playing with it right now in the yard!" Candace screamed.

"Okay, okay!" her mother yelled as she was dragged out the door.

Phineas and Ferb looked down at the door.

"I guess we can take it off the sniff setting. Let's put it on 'play' mode." Phineas pressed a button the dog.

"Sit." The dog did as he was told.

"Roll over."

"Go robot." The dog pretended to walk around clunky and robotic. Candace and Ms. Flynn-Fletcher walked out right when the dog was moving choppily.

"It just likes like one of those robotic dog toys, Candace," Ms. Flynn-Fletcher said.

"But-!"

"Did you boys invent this in science class?"

"Well, no. We were using Whiff to help us with our detective work," Phineas explained.

"Aw. That's really cute, boys. You can play with your robot dog for a while. I'm making dinner."

Candace looked like she was ready to scream. She shook her head. "It's Valentines Day. It's Valentines Day. It's Valentines Day," she told herself hoping that this would keep her mind off of the busting.

Perry peered around the gate to see Isabella next door hanging around a tree looking kind of melancholy.

"You know, Ferb. It's too bad we didn't get to figure out who left that secret admirer note. The hand writings were all good possibilities, but none of them I felt quite sure on. It's weird. Usually we're able to complete our missions by the end of the day. Oh well. I guess not _everything _can work out the way you planned," Phineas said.

"Take Candace's plans for example," Ferb said.

Perry made the connection right away with Isabella being sad and Phineas talking about a secret admirer note. He remembered he still had that second rose with him. He slipped upstairs when no one was looking and pulled out a price tag on a desk that had been left over from Ms. Flynn-Fletcher's antique store.

Outside, Phineas tossed a stick.

"Fetch! Good boy, Whiff. Hey, where's Perry?" Perry showed up and chattered.

"Oh, there you are Perry. What were you up to? Here. I'd like you meet, Whiff."

Over next door, Isabella sighed still feeling pretty disappointed. She turned to head in through her front door when she saw a rose with a tag on it on her doorstep. She picked it up. The tag read,

To: "Secret Admirer"

From: Phineas

Isabella's eyes grew wide. She made an enormous smile and ran next door.

Phineas looked up from giving Whiff a belly rub. He greeted, "Oh hi, Isabella. What-"

"I can't believe you figured it out! AND YOU'RE RIGHT! I AM YOUR SECRET ADMIRER! I LEFT YOU THE NOTE! IT'S ALL TRUE!" Isabella screamed with a mixture of joy and excitement.

"You were my secret admirer?" Phineas asked looking quite confused. He looked at Ferb who only shrugged.

"I love the rose, Phineas! Thank you sooooo much!" Isabella cried bouncing up and down. She completely ignored Phineas' question. Perry pretended to be asleep while he listened to every word of the conversation.

"Where did the rose come fr-" Phineas was cut off as Isabella kissed him on the cheek.

"This is the best Valentine's Day ever! Whoo-hoo!" Isabella skipped back to her house.

"Uh- Ferb? What just happened?" Phineas asked.

"Love," Ferb answered.

"Wow. So that's what love is like. Love's wet- and loud- and jumpy. So… Isabella's my secret admirer huh? Who knew?" Phineas said. "Well as long as she doesn't turn into Candace over Jeremy then I am completely cool with that."

Phineas tossed a tennis ball without giving what had just happened any other thought. "Go long, Whiff!" he called.

Perry, from under the tree, smiled at what he had done and fell asleep for real this time.

****

**Note: *Patty is from a past fanfic of mine. (P&F's Furry Friends Day Care Center).**


	7. Epilogue

Epilogue

Vanessa picked up the mail for her dad. She flipped through it and found a card for her. She opened it up and out popped confetti and her own personal lights show lighting up on a pop-out heart in the card. It spelled out, "HAPPY VALENTINE'S DAY, VANESSA!" She looked down in the corner and in small handwriting it was signed, 'F.F'. She smiled at it and said, "Same to you, Ferb."


End file.
